Chapter 12: EUKARYOTIC MICROBES

Transcription

1 Chapter 12: EUKARYOTIC MICROBES 1. Protista: Algae & Protozoa 2. Fungi 3. Helminths

2 1. Protista: Algae & Protozoa Chapter Reading pp , , ,

3 Overview of the Algae Characteristics of algae: unicellular or multicellular eukaryotes almost all are photoautotrophs (photosynthetic) all are essentially aquatic (live in fresh or saltwater) all are capable of asexual reproduction some are capable of sexual reproduction as well **produce an estimated 80% of O 2 in the atmosphere!**

4 Diatoms unicellular or filamentous (form multicellular filaments) have a unique cell wall structure composed of a carbohydrate called pectin & silica responsible for geometric, glass-like appearance widely distributed throughout photic zone important part of aquatic food webs

5 Dinoflagellates what are commonly referred to as plankton unicellular algae with 2 perpendicular flagella Cellulose plate Longitudinal flagellum Transverse flagellum some produce potent neurotoxins source of toxic algal blooms (e.g., red tide ) important part of the oceanic food web

6 Overview of the Protozoa Characteristics of protozoa: all are unicellular eukaryotes all are heterotrophs (a few can be photosynthetic) capable of asexual reproduction (some sexual reproduction) parasitic species have complex life cycles some form protective cysts as part of their life cycles Protozoan phyla we will consider: Parabasalids Apicomplexa Euglenozoa Diplomonads Ciliophora Amoebozoa

7 Parabasalids & Diplomonads do NOT have mitochondria have an analogous organelle called a mitosome most have multiple flagella, Diplomonads have 2 nuclei several parasitic genera can cause human disease Trichomonas, Giardia a Parabasalid a Diplomonad

8 Apicomplexa non-motile obligate intracellular parasites have a unique apical complex of fibers and vacuoles that release digestive enzymes aid in penetration of host animal tissue includes species of Plasmodium responsible for the disease malaria Nucleus schizogony Schizont Merozoites Multiple mitoses Cytokinesis P. vivax (inside RBCs)

9 Plasmodium Life Cycle (malaria)

10 Ciliophora ( ciliates ) all have many small projections called cilia used for locomotion & to direct food into the cytostome ( mouth ) some have multiple nuclei have contractile vacuole to expel excess water taken in by osmosis (expelled by exocytosis)

11 Conjugation 1 Mates couple. 2 Meiosis of micronuclei produces 4 haploid micronuclei in each. 3 Three micronuclei in each disintegrate, the remaining 2 replicate by mitosis. Compatible mates Macronucleus (50n) Micronucleus (2n) Haploid micronucleus (1n) 4 Mates each swap one micronucleus. Diploid micronucleus (2n) 9 Three cytokineses partition pairs of nuclei into four daughter cells. 8 Original macronucleus disintegrates. Four micronuclei become macronuclei, four remain micronuclei. 7 Three mitoses without cytokinesis produce 8 micronuclei. 6 Micronuclei fuse to form diploid micronucleus. 5 Partners separate.

12 Euglenozoa some are photosynthetic (Euglena) have a light-sensitive eyespot & a single flagellum includes the hemoflagellates (Trypanosoma) responsible for sleeping sickness & Chagas disease

13 Sleeping Sickness tse tse fly Chagas Disease kissing bug Trypanosoma brucei Trypanosoma cruzi

14 Amoebozoa aka amoebas have distinct form of locomotion called amoeboid movement extend cytoplasmic projections called pseudopods also used to engulf and ingest food by phagocytosis

15 2. Fungi Chapter Reading pp

16 Overview of the Fungi General characteristics: eukaryotic absorptive heterotrophs unicellular (yeasts) or multicellular (molds, club fungi) reproduce asexualy OR sexually cell walls that contain chitin vast majority are terrestrial (i.e., live on land) all fungi develop from haploid spores (no embryos) do NOT have flagella (spores are immotile) **study of fungi is known as mycology **

17 Structure of Multicellular Fungi The thallus ( body ) of a fungus consists largely of filamentous chains of cells called hyphae: vegetative (non-reproductive) or aerial (reproductive) some have septa (septate), some don t (coenocytic)

18 Hyphae form a Mycelium On a rich source of nutrients, many hyphae can be produced to form a continuous mass called a mycelium. vegetative hyphae spread across food source & absorb aerial hyphae grow vertically & produce spores in a number of different ways, depending on the fungus

19 Reproduction in Filamentous Fungi Can reproduce asexually by fragmentation: hyphae fragments grow by mitosis Produce spores asexually or sexually: Asexual spore production occurs at the tip of aerial hyphae derived from single parent fungus produced by mitosis Sexual spore production involves a partner of opposite mating type, meiosis

20 Asexual Spore Production sporangiospores are produced within an enclosed sac called a sporangium spores not enclosed in a sac are conidiospores (aka conidia) Sporangium Sporangiophore Conidiophore Conidia

21 Sexual Spore Production Sexual spores in fungi require 3 phases not seen in the production of asexual spores: 1) transfer of a haploid nucleus to a cell of the opposite mating type: plasmogamy (produces a dikaryon) 2) fusion of the haploid nuclei to form a diploid zygote nucleus: karyogamy haploid nuclei may reproduce by mitosis before fusing this is the ONLY occasion when fungal cells are diploid 3) meiosis to produce haploid sexual spores

22 3 Major Fungal Phyla Zygomycota conjugation fungi (molds) Basidiomycota club fungi (mushrooms, smuts, rusts, puffballs) Ascomycota sac fungi (yeasts, molds, truffles, lichens)

23 Zygomycota Asexual Reproduction Sexual Reproduction 2 Sporangium bursts to release spores 3 Spore germinates to produce aseptate mycelium (1n). 4 Vegetative mycelium grows. 7 8 Zygosporangium 9 Nuclear meioses occurs matures. (not shown). Zygosporangium forms. (2n) 10 Zygosporangium produces an asexual sporangium (1n). 6 Mating hyphae join and fuse. Dikaryon (n+n) Haploid nuclei (1n) 11 Spores (1n) are released from sporangium. 1 Sporangium (1n) Aerial hypha produces a sporangium. Sporangiospores Sporangiophore Gamete forms at tip of hypha. 12 Spore germinates to produce mycelium. have aseptate coenocytic hyphae, sporangia

24 Basidomycota Cross section of gill showing hyphae. 5 Pair of haploid nuclei fuse. 2n 6 Meiosis produces four haploid nuclei. 7 Four basidiospores (1n) develop. Gills Basidium 1 Basidiospore released. Button 2 Basidiospores germinate to produce mycelia Dikaryotic mycelium produces basidiocarp (mushroom). 3 Dikaryon (n+n) Hyphae of opposite mating types fuse belowground to produce dikaryotic mycelium.

25 Asexual Repr Sexual Reproduction 3 4 Vegetative mycelium grows. Conidiospore germinates to produce mycelium. 5 Hyphal tip undergoes cytoplasmic fusion with opposite mating type Dikaryon forms. septate hyphae 2 Conidiospores released from conidiophore. 7 Nuclei fuse in terminal cells to form 2n nuclei. Dikaryon asexual conidiospores Conidiospore 11 Conidiophore 1 Hypha produces conidiophore and conidiospores. Ascospores germinate to produce mycelia. 10 Ascus opens to release ascospores. Ascospores Ascus 8 Meiosis produces four haploid (1n) cells. sexual spores in an ascus Ascomycota 9 Mitosis produces eight haploid ascospores on each tip. includes the yeasts

26 Budding Yeasts Spherical unicellular fungi. reproduce asexually by budding also reproduce sexually facultative anaerobes (used for beer, wine ) Saccharomyces cerevisiae important in biological research studying the cell cycle production of insulin & other important things

27 Lichens Lichens are actually 2 different organisms in a mutualistic symbiosis: cyanobacteria or green algae living among the hyphae of an ascomycote (or basidiomycote) fungus gets free carbs! algae or cyanobacteria protected from elements important pioneers can grow on inorganic surfaces, begin succession

28 Lichen Structure Fungal hyphae form the following structures: protective cortex inner medulla where algae grow rhizines to attach to growth surface

29 3. Helminths Chapter Reading pp ,

30 Overview of the Helminths Helminths are parasitic worms found in 2 animal phyla, the Platyhelminthes (flatworms) and the Nematodes (roundworms). multicellular eukaryotic heterotrophs have complex life cycles frequently involving multiple hosts contain distinct organ systems some may be reduced or absent due to dependence on host (e.g., no digestive system, no locomotion)

31 Platyhelminthes (flatworms): typically hermaphroditic (monoecious) have a proctostome (single opening, no anus) we will look at 2 classes: Trematodes (flukes) & Cestodes (tapeworms) Nematodes (roundworms): typically dioecious (2 sexes) have complete digestive system (mouth & anus) we will look at 2 types: pinworms & hookworms

32 Trematodes (flukes) (liver fluke) Members of this class of flatworms are all parasites associated w/particular host tissues (liver, blood, lung) can have multiple larval stages and intermediate hosts hermaphroditic (monoecious) attach to host tissue via oral and ventral suckers absorb nutrients through outer cuticle

33 Fluke Life Cycle (blood fluke)

34 Tapeworms (cestodes) intestinal parasites scolex (head) has hooks & suckers for attachment no digestive system, absorb nutrients repeating proglottids have male & female reproductive organs (monoecious) mature proglottids detach & pass w/feces allowing transmission to other hosts

35 Typical Tapeworm Life Cycle

36 Pinworms entire life cycle in human hosts live in large intestine females lay eggs on anus Enterobius vermicularis a dioecious parasitic roundworm (nematode) transmitted to new hosts via eggs

37 Hookworms dioecious nematodes live, mate, lay eggs in small intestine eggs pass with feces, hatch in soil larvae enter new host through skin, pass to lungs via blood, lymph coughed up, swallowed to reach small intestine repeat life cycle cutting plates in mouth used for attaching to and removing host tissue

38 Hookworm Life Cycle

39 Key Terms for Chapter 12 thallus, hyphae, mycelium septate, aseptate, coenocytic conidia, sporangia plasmogamy, karyogamy, dikaryon zygospore, basidium, ascus saprophytic, monoecious, dioecious mitosome, cytostome, pseudopods scolex, proglottids Relevant Chapter Questions MC: 1, 4-5, 12, 1 Matching: 2 nd set Labeling: 1-2